1. Field of the Invention
The present invention relates to a semiconductor device. The present invention particularly relates to a semiconductor device capable of wireless data communication, a so-called IC chip (also referred to as an ID chip or a transponder) for RFID (radio frequency identification).
Note that the semiconductor device herein means all devices that can function by utilizing the semiconductor characteristics.
2. Description of the Related Art
In recent years, as it is called ubiquitous information society, an environment which is capable of accessing to an information network anytime and anywhere has been put into place. In such environment, an individual identification technique in which an ID (individual identification number) is given to an individual object to clarify records of the object so that it is useful for production, management, and the like has been researched for practical use. In particular, semiconductor devices which utilize an RFID (radio frequency identification) technique and performs wireless data communication with external communication devices (hereinafter referred to as communication devices, and also referred to as reader/writers, controllers, and interrogators) have become widely used. Such semiconductor devices are hereinafter simply referred to as semiconductor devices and also referred to as ID chips, IC chips, and transponders.
A semiconductor device receives a wireless signal transmitted from a communication device by an antenna. The antenna generates a signal of AC voltage (hereinafter referred to as an AC signal) by receiving the wireless signal. The AC signal is converted into a signal of DC voltage (hereinafter referred to as a DC signal) by a rectifier circuit which performs rectification. The DC signal is input to a constant voltage circuit (also referred to as a regulator or a power supply circuit) so that a power supply voltage Vdd is generated. The power supply voltage Vdd generated in the constant voltage circuit is applied to a plurality of circuits included in the semiconductor device.
In Patent Document 1 (Japanese Published Patent Application No. 2007-43568), a structure is disclosed in which, in order to increase energy efficiency of a wireless signal to be received by an antenna, a voltage of a DC signal is boosted by a boosting circuit with a charge pump, and the DC signal is supplied to an RF transmission circuit after electric power is accumulated in a charging/discharging circuit.